As never before, military, security, and law enforcement personnel employ sophisticated electronic equipment in the performance of their assigned tasks. Such equipment often incorporates a wide variety of panel displays and light indicators which serve to inform the user of system status or alert the user to dangerous conditions.
The use of such equipment, however, can pose serious problems when used by personnel operating in covert situations. Although the equipment may be necessary to accomplish the task at hand, the visible light radiation emitted from such panel light indicators may unfortunately be detected by hostile entities operating in or near the same area.
The problem is further magnified by the modern development of Generation III image intensifying devices, the most common of which is the night-vision goggle (NVG). Such devices permit an individual to see near-infrared and infrared radiation as visible light. Usually, equipment panel light indicators include incandescent lamps or light-emitting diodes (LEDs) which typically emit, in addition to visible light, some radiation in the near-infrared and infrared wavelength spectrum. Hostile forces equipped with night-vision goggles (NVGs) or similar equipment can easily detect equipment employing such light indicators.
Therefore, there is a need for light indicators which provide "secure" or night-vision compatible lighting. Secure lighting is defined as lighting that provides the operator with necessary system information, yet is not substantially visible to an aggressor using either an unaided eye or an image intensifying device.
Prior art panel light indicators cannot satisfactorily meet this "secure" requirement. Although the conventional wisdom has been to use shutter caps placed over the light indicators to selectively block the radiation, such a solution does not permit the user to be continuously apprised of necessary system information. Disadvantageously, the light indicator becomes fully detectable when the user opens the shutter to check a system parameter.